The U.S. Federal Communications Commission asked AT&T on Friday for a sound explanation for its decision to delay its Internet expansion in 100 cities due to net neutrality concerns.

Earlier this week, AT&T CEO Randall Stephenson made a fierce announcement that it is holding up the installation of high-speed fiber network in 100 cities in the United States, including Chicago, San Diego, San Francisco, Los Angeles, Cleveland and Miami. The infrastructure will allow consumers to access Internet speed as fast as 1 gigabit per second.

"We cannot be good stewards of our shareholders' capital and make these investments and not really understand how those are going to be regulated in three years, because these regulations that we're talking about are public-utility-style regulations, and this industry's moving fast," said Stephenson said at an analyst conference.

"And if you can't bring new products to service at your speed, not the government's speed, if you can't change prices at the market speed, not the government's speed, why would you ever make these investments? So we're on a pause mode right now."

Analysts predicted that AT&T's announcement will surely pressure FCC in its resolution. Instead, the federal agency emailed the telecom provider asking it to explain its outwardly threatening statement. AT&T has until Nov. 21 to respond.

The commission requested AT&T to submit all papers related to its decision for documentation and review. The FCC is still reviewing the AT&T-DirecTV merger proposal, and the installation of the high-speed fiber that will provide Internet connection to 100 cities is part of its approval requirement, according to Reuters.

AT&T did not directly comment about the request of the agency.

"We are happy to respond to the questions posed by the FCC in its review of our merger with DIRECTV. As we made clear earlier this week, we remain committed to our DIRECTV merger-related build out plans," AT&T said in a statement.